Thank you @JaneJones - I use savon de Marseille soap flakes for clothes washing but I got the impression that Savon Noir was different from the “normal” savon de Marseille. My partner said something about one using sodium and the other potassium but he wasn’t at all sure 
(PS I agree about vinegar and bicarb - I would add citric acid to the list though as I use that with bicarb for loo cleaning…)